In this instructable I will explain how I made my second bigger foundry yet again mostly constructed from scrap I collected and recycled it into something more usefull.
The biggest advantage of this design is that it has a very strong body made from an empty gas cylinder and the best part is that it will last for a long time, the only thing that might have to be changed or repaired is the inside refractory.
As I wrote on my last ible my aim is to create some aluminium sand casting of differrent objects.
At this stage I piled my aluminum ingots and did a few experiments with my foundry, some successful others went wrong which I have learned from. It is really exciting to create some new aluminium object knowing what it was in its former "life" cycle.
I will also try and explain a little bit about sand casting to my knowledge.
I am no expert it is all based on my hobby experience so I hope you enjoy it.

_____________________________________________________________________A few Saftey words: Coming into contact with fire and boiling melted metal can be very dangerous so always work safe using proper full body protection including respirator mask against toxic fumes and dust from mixing refractory materials. Never melt in a wet area or near water, if water comes into contact with the boiling aluminium it might "blow" in your direction.
The info in this instructable is based on my experience.
I disclaim any responsibility for any resulting damage, injury, or expense.
All use by you of this website is at your own risk, work safe.
_____________________________________________________________________

Excellent ible. Trouble is, now I don't know whether I want to make a stove for my workshop or a furnace suing the old gas bottle I have :)

I have a question if I may? Do you have any problems with the surface of your castings? I need to make some aluminium moulds (for pouring molten lead into for fishing weights) but they really have to be nice and smooth. Any ideas how I can achieve this?

Thank you I am happy you liked my ible. The best way to decide is which one will be more useful in the long run. Most of my castings are very good. I had of course some casting gone wrong but usually the reason is running out of aluminum, bad mould construction, porosity (small gas deefects, air holes) or just doing some experiments. I am using petrobond sand for my moulds and it's great sand to work with and to get very high quality finish.You are welcomed to visit my blog I have a few projects using sand casting. I believe you can get very good results using this type of sand and you can make a mould for many fishing weights in one pour. Just one thing and this is up to you to decide, I wouldn't melt any lead at all, Lead is a poisonous metal and can cause serious health problems especially among children. Link:Lead health effects If you have any questions I will be happy to answer thanks again.

I have to tend to agree with 'klincecum' here, sorry 'NutandBolt'. Most people who cast lead fishing weights do tend to do it outdoors or at least with very good ventilation anyway. So there's no real health concerns with it. I suppose there may be secondary risks from using scrap lead though. Unless you know for certain that the lead has not been used with nasty chemicals next to it. I'm thinking lead pipe work that is used for chemical transference. That could cause problems....

Hiya mate. Just noticed something, I am not 'suing' any old gas bottles :) I will be using them of course...

Anyway, Petrobond sand. Any idea what makes it special as opposed to ordinary sand. It sounds like a trade name and it's not one that I know of here in the UK. I was thinking of using what we call silver sand. This is a very fine and very clean sand that is used for children's sand (play) pits. It has to be fine, soft and ultra clean because of this. I'll add fuller's earth clay to this to create my moulding sand but don't yet know in what quantities.

Lead. Yep, nasty stuff but then so is aluminium fumes. Lead casting is quite common still over here in the UK and I will only be doing it outside. There are still an awful lot of houses that have lead water pipes ours included. Having once been a plumbing and heating engineer I can tell everybody that the danger from lead is real but very much overstated. It's bad if you ingest it in anyway and that does indeed include fumes, hence my proposing to cast the weights out of doors, it's safest that way.

Petrobond vs green sand. petrobond is oil-bonded casting sand, theoretically you can leave the sand in a closed container and it will be good for use years later. Also the final casting will be very high quality. The downside: it is expensive in comparison to green sand. Play sand is also good but you have to make sure you make a good mix ratio of the play sand+Bentonite(clay)+water (not too much water). Petrobond is available in the UK and is mostly sold in foundrys and less in hardware shops such as B&Q. I know that because the petrobond I have is made in the U.k. I am not promoting products but this is the link of the commpany in case you want to have a look. :-)

Big fan of the project! I'm thinking about doing it myself. Now, I know you mentioned what size bag of cement you got, but how much did you use? I'm trying to be economical and I want to get the smallest size I can for this design.

I've actually done the same thing (with a propane tank that is) Very nice job! I ended up scrapping most of it, because I couldn't get a decent enough mold to make it work. But I've never heard of petrobond. Then again, I built the whole thing for <$50 because I was on such a tight budget...

One thing I would recommend though is that you modify it a bit and put a propane burner in instead. Much easier than charcoal, and you have a more controllable heat. From the looks of yours, all you would have to do is insert a propane line into the blower pipe, and you're pretty much there. You would just need to add a flame holder, but that's fairly simple.

For decent molds, I would highly suggest trying out lost-foam casting. You can do it with junk Styrofoam and an X-Acto knife or something similarly sharp, and sand from your backyard. It's just about the cheapest and easiest method to produce fairly high-quality objects.

Wonderful ible! I just finished making a similar furnace and will be adding a hinge after seeing how nicely yours worked. I used regular portland cement and cured it for 18 days before firing. It is pretty thoroughly covered in hairline cracks after 4 firings and the outside gets terribly hot. I am guessing I will have to recast the cement before too long and am interested in fire cement. How well Is your refractory holding up? How many times have you fired it?

All I have to say it thank you so much. I just built my refractory/foundry almost exactly like yours. All I have left is to get ahold of some refractory cement and Im in business. This is awsome. You rock!

The sensor I used is a simple and trusted multimeter that I got on Ebay. All that is needed is to set the multimeter setting to tempature and place the tempature wire in the furnace. As for the ingots, I am using metal muffin tray (not teflon). All you have to do is pour the molten metal into it and you get a nice aluminum muffin. You can also make a container for the ingots DIY style like the one I welded from metal angles. I am using it to make slim ingots for my pipe cruicble. Thank you.

Nice technique with filling the gas cylinder with water! An elegant solution to the problem of flammables.

A professional iron worker once told me that cast iron cookware works well for a crucible. There are a variety of pans, pots, "dutch ovens" and other styles to choose from. Maybe there are cast iron muffin pans waiting to be found at a junk sale.

I have been warned about using cast iron cookware if it has not been cleaned of all rust. If I understood correctly, what I was told is the combination of rust and molten aluminum can form something akin to thermite (possibly thermite itself?). If this is the case it could be very dangerous.

Ferrous oxide (rust) and aluminium do make thermite. Although the exact ratio's are industry secrets for each company they boil down a lot of rust powder and a lot of aluminium powder mainly for surface area considerations (occasionally it is doped with magnesium to help things along). At any level of rust build up on a pot that doesn't affect it structurally I don't think you have much to worry about. I've never had a problem. but if your worried put the offending rusty item in the smelter with it going full bore for a few minutes (be careful cause this smelter can easily melt cast iron if you are using charcoal ... I speak from experience of loosing an entire melt to this whoops(!?!)) by the time the pot has a barely visible glow in normal light there will be no more rust on it.

My dad recently got several dead lawnmowers from junk heaps. I repaired the oldest one and we are restoring it but he tore the rest apart for the pistons and such that he uses to make statues.The rest of the mowers were set to be thrown out but I grabbed a large amount of aluminium pieces. Just testing my furnace i threw a chunk in and it melted beautifully and was quite strong when I later pulled it out.I recommend saving them and smashing the cast base into smaller pieces as well as the tougher engine pieces.

you might find this interesting. It's a link to a catalog website that has all sorts of antiquated methods for making things at home. pretty interesting. This page particularly deals with a book that you can order that shows you how to make a crucible.